Cooling of pistons



H. R. RICARDO COOLING OF PISTONS Filed Aug. 27, 1943 4 Sheets-Sheet 11 Nov. 7, 1944. H. R. RICARDO 2,362,158

I COOLING 0F PISTONS v I l Filed A ug. 27; 194s 4 sheets-sheet' 2 '4th rac/s l Nov. `7, 1944. H. R. 'RICARDO 2,362,158

COOLING 0F PIsToNs 4 SheetsjSl'xeetK 4 H. R. RICARDO ycooLING 0F PIsToNs Filed Aug.. 27, 1943 Nov. 7, 1944.

/y/f M v A F/G./4. c/ J5 'In Fen H In outer part and between it and the periphery of to the piston axis. f

Patented Nov.I 7, 1944 11am Ralph Ricardo, London, England Application August 27, 1943, Serial No. 500,280 In Great Britain July 20, 1942 1o claims.

This yinvention relates to the cooling of pistons and particularly pistons of a known type in which ,the piston is made in two parts, namely an inner member which carries the gudgeon pin, and an outer part comprising the crown andskirt within which the inner member is secured by bolts passing through the crown. 'Ihe object of the invention is to provide a construction in which a cooling of the crown and gas pressure rings can be effected by means of lubricating oil which is caused to be delivered through the connecting rod. l

According tolthis invention radial grooves are provided in that face of a part forming 'a disclike crown of the innerpart of the piston' which lies against the inner face of the crown of the outer part and these grooves lead into an annular space or chamber which is arranged within the the inner part so that oil which is caused to flow 20 from the engine crankshaft through the connecting rod into these radial grooves will pass into this annular space and having effected the desired cooling can ow away between the exterior of the inner part and the inner surface of the outer part of the piston. The grooves in the face of the inner part or member radiate from a central opening into which open one or more pas. sages in the small end of the connecting-rod .30 through which oil can issue which has been caused to iiow through a longitudinal passage in the connecting rod. 'I'he annular space between the` inner and outer parts of the piston is so formed in the outer part that it extendsbehind all the external grooves which carry the gas pres- 3 sure rings on the outer part in order that a. cool-v ing of these rings shall be eilected. The outer part ofthe piston comprising the crown and the skirt is Wholly turned and is symmetrical about the piston axis being circular and of uniform thickness circumferentially in any plane normal In order to prevent leakage and ensure'v that all pass from the small end of that rod into the central passage through the inner part of the piston,

it is Adesirable to provide a, spring-loaded telescopic tubular connection forming an oil collector between theI passage through the crown of that 50 part of the piston and the hole through which the "oil issues from the vsmall-end of the connecting rod. This oil collector conveniently cornprises a tubular plug inserted through the upper face of the crown of the inner part ofthe piston f 55 (C l. 12s-176') and a tubular member which can slide telescopically either on'or in the lower or outer end of the plug and is maintained by the action of a` spring in contact with the surface of the adjacent Vend of the connecting rod. Such a spring-loaded oil collector is especially required in the case where the improved piston is used in an internal Ycombustion engine operating on the four-stroke secured together by bolts which are passed through the crown oi the outer part and through ,a disc-like part or crown ofthe inner member which lies against the inner side of the crown. The inner member is supported laterally by a rib which projects from 'the lugs which carry the gudgeon pin and lies within a corresponding inwardly projecting annular rib within the skirt portion of the outer part of the piston. There is such clearance between these engaging projections that oil can leak away between them after it has performed its cooling on the piston.

I vThe accompanying drawings illustrate by way of example how the invention may be carried' out in practice. In these drawings- Figure 1 is a longitudinal sectional elevation of the complete piston, the section being taken in the plane which contains 'both the axis of the piston and also the axis of the gudgeon pin.`

Figure 2 is a similar view, but the section is taken in a plane at right angles to the plane of the section in Figure 1 that is to say in a plane normal to the gudgeon pin axis.

Figure 3 is a sectional elevation of the inner part of the piston as seen in Figure 1, but shown by itself. L

' Figure 4 is a similar view of the inner part of the piston, but the section is taken in the same plane as the section shown in Figure 2. a

Figure 5 is a plan of the inner part when re- A moved.

the oil flowing through the connecting vrod will 45 Figure 6 is an under side view of the same part and as seen in Figure 4.

Figure 7 is a sectional elevation of the cute part of the piston-as seen in Figure 1, fbut shown by itself.

Figure 8 is a side elevation of the inner part as l,lirst turned up and before cutting away portions on the line 9 9 in Figure 10, that is in a plane normal to the crankshaft axis and showing a somewhat modied formation of the inner part of the piston.

Figure is a similar section taken on the line lU-I l] in Figure 9.

Figure 11 is a side elevation of the crank pin showing the oil passage through its wall.

Figure l2 is a transverse section of the crank pin on the line |2-I 2 in Figure 11.

Figures 13 and 14 are longitudinal sectional elevations in planes at right angles, and similar to Figures 1 and 2, but showing a modified arrangement of the oil collector between the small end of the connecting rod and the crown of the inner part of the improved piston.

The outer part of the piston comprises the crown A, the ange A1 in which are the grooves A2 vfor the gas pressure rings, and the skirt A3. Within the skirt of this part of the piston is an annular rib A1 and between this rib and the l crown A are two annular recesses B and B1 of which the former is formed in the flange A1 around a part A5 which is thus caused to project on the inner side of the crown and has a hat face. This recess B also lies behind the grooves A2 and has between it and the rib A1 the other recess B1 which is surrounded by a part of the skirt A3. The separate inner part of the piston in itself somewhat resembles a piston having a disc forming a crown C with a at face which lies in contact With the fiat face 0f the part A5 and in which are a series of grooves C1 radiating from a central opening C2. When this inner part is in place in the cuter partthe periphery C3 of the crown C of the inner part lies just clear of the inner surface of the flange A1 of the cuter part so as to leave an annular gap D which serves as a communication between the inner annular recess B and the other annular recess B1 as can be clearly seen in Figures 1 and 2. The crown C has a skirt-like part C4 having on its exterior an annular rib C5 of which portions are cut away as at C6, see Figure 6. The projecting parts of this rib C5 lie in contact with the inner face of the annular rib A4 within the skirt of the outer part of the piston when the whole is assembled thus giving lateral support for the inner part. A

- recess B2 in the skirt C1 between the periphery C3 of the crown C and the rib C5 cooperates with the recess B1 within the outer part of the piston to form an annular chamber with which as mentioned the recess B is in communication through the gap D. Thus oil passing up through the opening C2 can travel by way of the radial grooves C1 into the annular chamber constituted by the recess B and thence through the gap D constituting a constriction into the annular chamber B1 B1, and from there it can passv through the spaces Cs in the rib C5 into the outer part of the skirt A3.

The innerpart C has -lugs E projecting or formed from the skirt C'1 and in these lugs are bearings E1 for the gudgeon pin F. Bolts G extending from the crown A of the outer part run through these lugs and serve to rigidly connect together the two parts of the piston.

On its under side the part of the crown C of the inner part around the central opening C11 1s formed as at C7 with a, seating to engage the outer surface of the small end of the connecting rod H. According to the external nish of the latter this seat may be cylindrical or spherical, but preferably it is cylindrical as shown in the drawings. The oil which is caused to come` up in the passage H1 which runs through the connecting rod H flows round in a groove H2 within the small end to an outlet opening H3 and thence by way of the central opening C2 and radial grooves C1 in the crown C of the inner part to effect a cooling of the crown A of the outer part, the rings in the grooves D and the skirt A3.

In the modified construction shown in Figures 9 and 10, the seating for the small end of the connecting rod about the central opening in the crown C of the inner part of the piston is constituted by an inserted tubular plug J the upper end of which is flanged at J1 externally and the flange seats in a recess around the opening in the face of the crown C. The inner end of the tubular plug J, which serves as an oil collector, lies in contact with the surface of the small end of the connecting rod. In the flanged end J1 radial notches or grooves J2 are formed to register with the ends of the radial grooves C1 in the at face of the crown C so that the oil coming up through the opening H3 in the end of the connecting rod H can pass through the bore J3 in the member J and by way of the grooves C1 into the annular chambers B and B1.

'I'he oil ilow from the crankshaft up through the connecting rod H is ensured in some known manner such as is commonly designated a timed delivery in that the delivery can take place only while the crank pin is moving between determined angular positions so arranged that oil can enter the connecting rod only while the inertia forces on the oil are acting ln a direction towards the piston. Alternatively, a'non-return valve may be arranged in the passage H1 through the connecting rod, this valve for example being in the form of a disc which is disposed in a recess in the end of the passage H1 near the big-end, the seating of the valve being in a removable plug. A convenient arrangement, however, to eiect a timed delivery is shown in Figures 9, 10, 1l and 12. Oil is forced in the usual manner through the hollow crankshaft K into the interior of the crank pin L which has a, radial hole L1 through its wall opening into a groove L2 which runs for a short distance circumferentially in the surface of the crank pin. The hole L1 runs at right angles to a line joining the axes of the crank pin and the crankshaft. In the bearing shell M there are holes M1 opening into a groove N which extends in the circumferential direction within the big-end H4 for a determined distance and terminates in the end of the passage HI. The direction of rotation of the crankshaft is indicated by the arrow O in Figure 9. It will be seen that oil can only ow from within the crank pin L into the passage H1 while the hole L1 is passing through an angular position in which this hole registers, through the holes M1 in the bearing shell, with the circumferential groove N. The left hand crank pin shown in Figure 9 is j ust approaching the angular position in which oil can begin to flow to the passage H1, while the right hand crank pin is in a position wherein the hole L1 is nearing the end of the groove N, when the flow of oil will be cut off.

By this means oil is caused to ow intermittently up through the connecting rod and into the annular chambers or spaces B B1, and the space B is kept at least partially filled with oil by reason of the resistance to the free flowing away of the oil caused bythe narrow annular gap D. This gap is arranged in a, place which lies behind the lowest of the grooves A2 or as shown in the drawings in a plane normal to the piston axis which lies below but near this lowest groove.

assauts ,crown and symmetrical about the piston axis by Bykeeping the annular space or chamber B partially lledwith oil this oil is shaken about there by Lthe movement yo1' the piston and thus caused to come into intimate contact with the metal forming the walls of this space. From the chamber B1 the oil is discharged downwardly past the annular rib A4,4 the latter defining a second annular gap which retards discharge of ,oil from chamber B1.

From two of the radial grooves C1 holes P run into the gudgeon pin bearings in the lugs E.

In the modied construction shown in Figures 13 and 14 there is provided a spring-actuated oil collector between the inner part C of the piston and the small end of the connecting rod H, an arrangement which is particularly desirable where the improved piston is employedl in an engine operating on the four-stroke cycle so as to obviate leakage of oil at this place. In this construction the tubular plug J4 has an `external diameter appreciably less than the internal diameter ofthe central hole CG in the crown C of the inner part of the piston. The plug is centered in this hole by the flange J5 at its upper or inner end which lies in and engages an annular recess formed in the face of the crown. This end of the plug has radial notches to register with the ends of the radial grooves C1 in the face of the crown. On the main cylindrical part J4 of the piug nts and can slide telescopically a tubular member Q which thus lies in the annular space in the hole C6 around the plug J4. At its outer end this sliding member Q has an external flange Q1 which also extends partially internally where there `is a diametrical slot Q2 adapted to register with the hole H3 through which the oil issues from the small end of the connecting rod. The end face of the sliding member Q is curved to lie in contact with the cylindrical surface of the end of the connecting rod.4 These parts are maintained in contact by the action of a coiled spring R which surrounds the sliding member 'Q and lies between its end ange Q1 and the adjacent face of the crown C of the piston part. This arrangement avoids the tendency for the collector to be lifted out of conturning and having uniform thickness radially in any plane normal to the piston axis, at least one circumferential groove in the exterior of the skirt of this outer part this groove being adapted to contain a piston ring, an inner member comprising a crown, a skirt and within the latter lugs in^which are bearings for the gudgeonpin, grooves radiating from a central opening in the otherwise flat face of the crown of the inner member, means by which the inner member is connected to the said outer part with the grooved face of the crown of the inner member in contact with the flat inner face of the crown oi the outer part, an annular chamber within the said outer part located where at least a part of this chamber lies behind the said piston ring grooves, this chamber lying between the outer part and the periphery ofthe. said inner member into which chamber lead the outer ends of the said radial grooves, and means by which oil flowing from the engine crankshaft through the connecting rod is caused to pass from the latter into and up the said radial grooves into the said annular' chamber whence the oil passes away between the skirts of the outer part and of the inner member.

2. A piston comprising in combination an outer part constituted by a crown the underside oi which is fiat and a skirt formed integral with the crown and symmetrical about the piston axis by turning and having uniform thickness radially in any plane normal to the piston axis, an inner member comprising a crown, a skirt and within lthe latter lugs in which are bearings for the gudgeon pin,. grooves radiating from a central opening in the otherwise nat face of the crown of the inner member, at least two annular parts and at least in part lying in contact with the lntact with the end of the connecting rod as may If found desirable Where the inner part of the piston is made from a metal such as an aluminium alloy having a high coefiicient of expansion, the bolts G by which the two parts of the piston are connected together, are preferably made from a ferrous alloy which also has a high coeiiicient of expansion.

The improved construction of piston has cer.

tain advantages arising in the rst place from the form of the outer part. Since this is completely symmetrical, circular and of uniform thickness in any plane normal to its axis, this part may be produced by turning. Secondly, owing to this symmetrical formation the risk of distortion due to heat effects is avoided. Thirdly by reason of the two-part construction there is an absence of stress transmission through the outer member as might result from gas loads on the crown of the piston.

What `I claim as my invention and desire to secure by LettersPatent is:

1. A piston comprising in combination an out-er part constituted by a crown the underside of which is at and ay skirt formed integral with the spaced apart on the exterior of the inner member these parts being respectively adjacent to terior of the skirt of the said outer part, means by which the inner member is connected to the said outer part with the grooved fa'ce of the `crown or" the inner member in contact with the at inner face of the crown of the outer part, an annular chamber within the said outer-part and between it and the periphery of the said inner member into which chamber lead the outer ends of the said radial grooves, and means by which oil flowing from the engine crankshaft up the connecting rod is caused to pass from the latter into and through the said radial grooves into lthe said annular chamber whence the oil passes away between the skirts of the outer part and of the inner member.

3. A piston comprising in combination an outer .part constituted by a crown the underside of which is at and a skirtformed integral with the crown and symmetrical about the piston axis by turning and having uniform thickness radially in any plane normal to the piston axis, an inner member comprising a crown, a skirt and Within the latter lugs in' which are bearings for the gudgeon pin, grooves radiating from a central opening in the otherwise flat face of the crown of the inner member, bolts passing through the crown of the said outer part and through the said inner part and serving to 'connect the inner member to the o uter part with the grooved face of the crown of the inner member in Contact with the inner face of the crown of the outer part, an annular chamber within the said outer part and between itand the periphery of the said inner member into which chamber lead the outer ends of the said radial grooves, and means by which oil flowing from the engine crankshaft up the connecting rod is caused to pass from the latter into and through the said radial grooves into the said annular chamber whence the oil passes away between the skirts of the outer part and of the inner member.

4. A piston comprising in combination an outer part constituted by a crown the underside of which is hat and a skirt formed integral with the crown and symmetrical about the piston axis by turning and having uniform thickness radially in any plane normal to the piston axis, an inner .member comprising a crown, a skirt and within the latter lugs in which are bearings for the gudgeon pin, a central opening in the crown of this inner member, a bearing surface within this part about the said central opening against which surface lies the gudgeon pin end of the connecting rod, grooves in the otherwise iiat face of the crown of the inner member, these grooves radiating from the said central opening in this crown, means by which the inner member is connected to the said outer part with the grooved face of the crown of the inner member in contact with the flat inner face of the crown of the outer part, an annular chamber within the said outer part and'between it and the periphery of the said inner member into which chamber lead the outer ends of the said radial grooves, and means by which oil owing from the engine crankshaft up the connecting rod is caused to pass from the latter and the said central opening in the crown of the said inner member into and through the said radial grooves into the said annular chamber whence the oil passes away between the skirts of the outer part l and of the inner member.

inner member which lies adjacent to but not in.

contact with an annular part of the interior of the skirt of the outer part and forming therewith an annular chamber within the said outer part and between it and the periphery of the said inner member into which chamber lead the outer ends l of the said radial grooves, an interrupted annular rib on the exterior of the inner member which is spaced apart from said peripheral part of the crown of that member this rib being at least in vpart in contact with an annular rib within the skirt of the outer part and forming therewith a second annular chamber between the inner member and the outer part, and means by which oil flowing from the engine crankshaft up the connecting rod is caused to pass from the latter into and through the said radial grooves into the said first annular chamber whence the oil passes away through the said second annular chamber and between the skirts of the outer part and of the inner member.

6. A piston comprising in combination an 'outer part constituted by a crown the underside of which is at and a skirt formed integral with the crownand symmetrical about the piston axis by turning and having uniform thickness radially in passes away between the skirts of any plane normal to the piston axis, at least one circumferential groove in the exterior of the skirt of this outer part this groove being adapted to contain a piston ring, aninner member comprising a crown, a skirt and within the latter lugs in which are bearings for the gudgeon pin, grooves radiating from a central opening in the otherwise flat face of the crown of the inner member, at least two annular parts spaced apart on the exterior of the inner member these parts being respectively adjacent to and at least one of them in part lying in contact with the interior of the skirt of the said outer part, means by which the inner member is connected to the said outer part with the grooved face of the crown of the inner member in contact with the flat inner face of the crown of the outer part, an annular chamber within the said outer part located Where at least a part of this chamber lies behind the said piston ring grooves this chamber lying between the outer part and the periphery of the said inner member into which chamber lead the outer ends of the said radial grooves, and means by which oil flowing from the engine crankshaft up the connecting rod is caused to pass from the latter into and through the said radial grooves into the said annular chamber whence the oil passes away between the skirts of the outer part and of the inner member.

7 AA piston comprising in combination an outer part constituted by a crown the underside of which is flat and a skirt formed integral with the crown and symmetrical .about the piston axis by turning and having uniform thickness radially in any plane normal to the piston axis, at least one circumferential groove in the exterior of the skirt of this outer part this groove being adapted to contain a piston ring, an inner member comprising a crown, a skirt and within the latter lugs in which are bearings for the gudgeon pin, a central opening in the crown of this inner member, a bearing surface within this part about the said central opening against which surface lies the gudgeon pin end of the connecting rod, grooves in the otherwise nat face of the crown of the inner member, these grooves radiating from the said central opening in this crown, means by which the inner member is connected to the said outer part with the grooved face of the crown of the inner member in contact with the fiat inner face of the crown of the outer part, an annular chamber within the said outer part located where at least a part of this chamber lies behind the said piston ring grooves this chamber lying between the outer part and the periphery of the said inner member into which chamber lead the outer ends of the said radial grooves, and means'by which oil owing from the engine crankshaft up the connecting rod is caused to pass from the latter through the said bearing surface and the said central opening in the said inner member into and through the said radial grooves into the said annular chamber whence the oil the outer part and of the inner member. A'

8. A piston comprising in combination an outer part constituted by a crown the underside of which is flat and a skirt formed integral with the crown and symmetrical about the piston axis by turning and having a uniform thickness radially 1n any plane normal to the piston axis, at least one circumferential groove in the exterior of the skirt of this outer part this groove being adapted to contain a piston ring, an inner member comprising a crown, a skirt and within the latter lugs in which are bearings for the gudgeon nin.

grooves radiating from a central opening otherwise at face oi' the .crown of the inner member, a peripheral parto! the innermembe'r which lies adjacent to but not in contact with an vannular part. of the 'interior of the skirt of the outer-f part and forming therewith an annular chamber within the said outer part locatedl between it and the periphery of the said inner l member where atleast a of this chamber lies behind` the said piston ring grooves and with the outer ends of the-said radial'grooves leading into this chamber, an interrupted annular rib on the exterior of the inner member which is spaced apart from the said peripheral part of the crown vof that member this rib being at least in part in contact lwith an annular rib within the skirt'of the outer part and forming therewith a second annular chamber between the inner member and the outer part, and means by which oil `iiowinir' from the engine .crankshaft up the connecting rodiscausedtopassfromthelatterintoad .Nthrollgh the lsaid radial grooves into the said rst annular chamber whence the oil passes away in the 'c crown o! the inner 'member and grooves radiating from this opening in the otherwise ilat face oi.'

this crown, means by which the inner memberY is connected tothesaid outer part with the grcoved outer part, an annular chamber within the said face of the crown of the inner member in contact with the hat inner face of the crown of the outer part and between it and the periphery' of the engine crankshaft; andayielding tubular conthrough the said second annular chamber and between the skirts of the inner member. l

9. A piston comprising in combination an outer part constituted by acrown the underside of which is ilat and a skirt formed integral with the crown and symmetrical about the piston axis by turning and having a uniform thickness radiouter part and of the ally in any planenormal to the piston axis,an

inner member comprising a crown, a skirt and within the latter lugs in which arebearingsfor the sudseon pin, a central g e through-the Y connecting the s aid inner member into which lead the outer ends of the said radial grooves'. a connecting rod to the smalLend of which oil flows up the `rod from collector is constituted by a tubular plug inserted in the said central 1 1- through the crownof the said innerpiston member, a tubular member which can slide telescopically on the tubular plugwith its outer end bearing on the surtaeelot the small end of the connectingfrod wherein is an opening through which issues the oil up the connecting rod, and a springwhich maintains the end oi the said tubular member in contact with the said surface ofthe small endoithe A naaaramnarosano. 

